That is the exact same mistake people make when they go buy a car. It is also the thinking that got us in this mess. They look at what their monthly payment is and not what they are paying.
Your friend needs to think about how big the hook she is on is.
She can be on the hook for $540,000 with a payment of $3500 month today. Or wait and only be on the hook for $440,000 (20% drop) and still have a payment of $3500 IF interest rates shoot up to 9.5%.
The difference is how easily she can walk away.
IMHO, the rate game is much less risky than the capital loss game of buying today.